This program project grant supports a clinical and laboratory program for a 20-bed intensive care facility with emphasis on the treatment of hematologic disorders by marrow transplantation. Principle priority has been on treatment of patients with acute leukemia or aplastic anemia. Total body irradiation and/or high dose chemotherapy is utilized to condition the patient to accept the graft and to eliminate malignant cell populations. Supportive therapies include granulocyte and platelet transfusions, laminar air flow isolation, gut sterilization and sterile diets. Immunologic recovery is monitored with long-term follow up. Supporting laboratories provide information in the areas of pathology, virology, microbiology, hematology, cryobiology, cytogenetics and histocompatibility typing. Research areas include prevention and treatment of graft-versus-host disease, opportunistic infections, acceleration of immunologic recovery and prevention of recurrent leukemia, application of immunotherapy to antileukemic treatment, in vitro assays of hematopoiesis and problems dealing with transplantation between donor-recipient non-HLA indentical pairs. Data processing and biostatistic functions provide maximum utilization of information generated.